Hey Hung-Te,
I had a bit of time to look into this and the patch actually came out fairly simple: https://chromium-review.googlesource.com/383966

In the current patch it's implemented as a separate option, --wp-layout-range (I'm open to suggestions for name). We might be able to overload --wp-range to accept either format (start & length or region name), but that may depend on getopt_long() behavior.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromiumos/third_party/flashrom/+/e8c9d1a07ecdf7e09814e2a5962eec9623710f91

commit e8c9d1a07ecdf7e09814e2a5962eec9623710f91
Author: David Hendricks <dhendrix@chromium.org>
Date: Sat Oct 29 03:11:52 2016

Add fmap regions to internal layout earlier

This makes flashrom search for an fmap and add its regions earlier.
The follow-up patch introduces a command-line option which depends
on this behavior.

BUG= chromium:635241 
BRANCH=none
TEST=tested with follow-up patch

Change-Id: I763f4dcdd5ab6d947ad59776931f42d31c2a253c
Signed-off-by: David Hendricks <dhendrix@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/405109

[modify] https://crrev.com/e8c9d1a07ecdf7e09814e2a5962eec9623710f91/flash.h
[modify] https://crrev.com/e8c9d1a07ecdf7e09814e2a5962eec9623710f91/cli_mfg.c
[modify] https://crrev.com/e8c9d1a07ecdf7e09814e2a5962eec9623710f91/flashrom.c

The following revision refers to this bug:
  https://chromium.googlesource.com/chromiumos/third_party/flashrom/+/c36685af7ab9976c03f3cc3b389d3ff43959f136

commit c36685af7ab9976c03f3cc3b389d3ff43959f136
Author: David Hendricks <dhendrix@chromium.org>
Date: Tue Sep 13 03:41:05 2016

cli_mfg: Add option to specify write-protect range by region name

This adds a new command-line option, --wp-region, which sets the
write-protect range using a region name instead of a numeric
range and length.

BUG= chromium:635241 
BRANCH=none
TEST=on system with w25q128 (16MB flash), tested --wp-region
using fmap region names (SI_DESC covering 0-4k and WP_RO covering
0-4M) as well as using layout regions (e.g. "-i layout.txt
--wp-region region0").

Change-Id: I6a3087053f655ef0337d018baefc9d222df658d2
Signed-off-by: David Hendricks <dhendrix@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/383966

[modify] https://crrev.com/c36685af7ab9976c03f3cc3b389d3ff43959f136/layout.h
[modify] https://crrev.com/c36685af7ab9976c03f3cc3b389d3ff43959f136/layout.c
[modify] https://crrev.com/c36685af7ab9976c03f3cc3b389d3ff43959f136/cli_mfg.c

Relevant doc to follow-up with: https://docs.google.com/document/d/10bJhjHeqENNdJVAl9scf_c6xBrthk2ru9PchgDEzeiw/edit#heading=h.kcogqanht8m8

cool, thanks!

I'll try to migrate factory code to use the new syntax in future.